Computer Fundamentals

Howard Aiken designed the Harvard Mark I (IBM Automatic Sequence Controlled Calculator), which was the first fully automatic calculating machine. UNIVAC I was the first commercial computer, EDVAC used stored-program architecture, and ENIAC was the first general-purpose electronic digital computer.

Third generation computers (1965-1970) were characterized by the use of integrated circuits (ICs), which replaced the discrete transistors used in second generation computers. Vacuum tubes were first generation, and SSI (Small Scale Integration) is a type of IC, not a device category itself.

Decimal 24 converts to binary 11000 using powers of 2: 1×16 + 1×8 + 0×4 + 0×2 + 0×1 = 24. This follows the standard conversion method of finding which powers of 2 sum to the decimal number.

Interpreters process source code line by line, translating and executing each statement before moving to the next. This differs from compilers, which translate the entire program into machine code before execution. The "line wise" option accurately describes this sequential processing.

NAND gates are called universal gates because any Boolean function (AND, OR, NOT, etc.) can be implemented using only NAND gates. NOR gates are also universal, but AND, OR, and NOT gates individually cannot implement all Boolean functions by themselves.

PC-AT stands for Personal Computer Advanced Technology, referring to IBM's PC/AT model released in 1984. The "AT" designation indicated it used Intel's 80286 processor and represented a significant advancement over the original PC architecture.

Daisy wheel printers are letter-quality printers that produce output by striking a character element (resembling a daisy with petals) against a ribbon. They are classified as letter printers because they print one character at a time, unlike line printers (which print entire lines) or page printers (which print entire pages).

EBCDIC (Extended Binary Coded Decimal Interchange Code) is an 8-bit character encoding system, which means it can represent up to 2^8 = 256 different characters. This was developed by IBM for their mainframe systems and provided sufficient capacity for letters, numbers, and special characters.

ASCII (American Standard Code for Information Interchange) is the most widely used character encoding standard for information interchange between terminals and computers. BCD is for numeric representation, EBCDIC is IBM-proprietary for mainframes, and Hollerith is an obsolete punched card code.

MICR (Magnetic Ink Character Recognition) is primarily used in banking for processing checks and other financial documents. The special magnetic ink allows machines to read account numbers and routing information even when printed over, making it essential for automated check processing.

The hexadecimal number system uses base 16, meaning it has 16 digits: 0-9 and A-F (representing 10-15). This base is chosen because it conveniently represents binary data (each hex digit equals 4 bits), making it useful in computing.

OMR (Optical Mark Recognition) scanners are designed to detect marks made by pencils or pens on paper, such as filled bubbles on answer sheets or survey forms. OCR reads printed text, BCR reads barcodes, and MICR reads magnetic ink characters - none of these detect handwritten marks.

A half adder is a digital circuit that adds two binary digits (bits) and produces a sum and carry output. It operates on only 2 bits at a time, unlike a full adder which handles three inputs including carry-in.

Binary 101.101 = 5.625. The integer part 101 = 1×4 + 0×2 + 1×1 = 5. The fractional part .101 = 1×(1/2) + 0×(1/4) + 1×(1/8) = 0.5 + 0.125 = 0.625. Sum = 5.625.

Laser printers use electrostatic charges and toner to create images without physically striking the paper, making them non-impact printers. Dot matrix, daisy wheel, and drum printers all use impact mechanisms with a ribbon striking the paper.

Telephone lines use serial transmission mode where data is sent sequentially, one bit at a time, over a single channel. Parallel transmission requires multiple simultaneous paths, which standard telephone infrastructure doesn't support.

In binary computing, 1 kilobyte = 1024 bytes (2^10), not 1000 bytes as in decimal systems. This follows the binary system where storage units double: 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024.

A bit (binary digit) is the fundamental unit of computer memory, representing a single 0 or 1. All larger units like bytes, KB, and MB are composed of multiple bits. A byte equals 8 bits.

ARPANET (Advanced Research Projects Agency Network), created by the US Department of Defense in 1969, was the direct precursor to the modern Internet. It pioneered packet-switching technology and TCP/IP protocols that evolved into today's Internet.

ENIAC (Electronic Numerical Integrator and Computer), built in 1945, contained approximately 18,000 vacuum tubes. This massive number contributed to its enormous size of about 1,800 square feet and high power consumption of 150 kilowatts.

The system unit houses the CPU, RAM, motherboard, and storage devices - all components that actually process and store data. Without it, peripheral devices like keyboard and mouse have nothing to control.

Boot sector viruses specifically infect the boot sector of hard disks and other storage devices. They execute during the system boot process before the operating system loads, giving them early system access and making them difficult to remove.